Netanyahu's comments, at a meeting of his Likud Party outside of Jerusalem, come as he plans to address the U.S. Congress on the nuclear negotiations.

The West fears Iran could build an atomic bomb with its nuclear program. Iran says its program is for peaceful purposes. The Islamic Republic is now negotiating a final deal with the U.S., Britain, France, Russia, China and Germany, with hopes of on a preliminary deal in March and a follow-up pact in June.

Netanyahu, as well as many in Israel, view a nuclear-armed Iran as a threat to its very existence, citing Tehran's repeated calls for Israel's destruction and its support for groups like Hezbollah.

In his remarks, Netanyahu said that the greatest challenge Israel faces is "the threat of Iran arming itself with nuclear weapons with a declared goal of annihilating us."

"From the agreement that is forming it appears that they (world powers) have given up on that commitment and are accepting that Iran will gradually, within a few years, develop capabilities to produce material for many nuclear weapons," he said. "They might accept this but I am not willing to accept this."

Netanyahu's remarks come amid an uproar over his upcoming visit to Washington. He accepted a Republican invitation to address Congress about Iran in early March, but the speech has angered the Obama administration because it was arranged without consulting the White House, a breach of diplomatic protocol.

Relations between Netanyahu and the White House always have been tense. His planned speech also has drawn fire in Israel, coming just two weeks before national elections. Netanyahu has rejected the criticism, saying it is his duty to lobby against the nuclear deal.